The present disclosure relates to a hovercraft or air cushion vehicle (ACV) that moves above a surface of the ground or on water on a cushion of air. More particularly, the present disclosure relates to an improved lift air supply system and method for a hovercraft.
Hovercraft or ACVs are well known. Hovercrafts typically include a bellows or inflatable skirt around a perimeter of the vehicle to define an inner lift region or air chamber under the vehicle. The skirt traps air from an air supply source, such as a propeller, to create lift. The lift of this pressurized air causes reduced friction which, in turn, reduces the energy required to propel the vehicle. Hovercraft typically use one or more engine driven propellers to create the lift and one or more engine driven propellers to create thrust to propel and steer the vehicle.
Surfaces over which hovercraft are driven are not always smooth and flat and loads on the hovercraft is not always balanced. There are often uneven surfaces and bumps to navigate. Therefore, the skirt around the perimeter of the hovercraft is flexible to allow it to conform to the irregularities of the surface on which the hovercraft is traversing. Even with a flexible skirt, there are irregularities that are too small or too large for the skirt to follow.
A hovercraft achieves minimal resistance when the surface it is traversing is perfectly flat. As the surface becomes more irregular, low areas allow too much lift air to escape under the skirt and high areas cause the skirt to drag on the surface thereby increasing friction. Problems occur when the same air supply used to provide lift air is also used to inflate the skirt. A specific engine and propeller combination always has a limited amount of air at any given pressure. As the surface area becomes more irregular, the lift pressure within the inner lift air chamber falls as the amount of air escaping under the skirt increases. If the lift pressure and the skirt pressure are from the same source, then the skirt pressure is also reduced when the pressure in the inner lift air chamber falls, thereby causing the skirt to deflate and allowing the center of the hovercraft's hull to touch the ground or surface of the water. This causes friction to increase.
One solution to this problem is to provide an alternate source of pressurized air to the skirt. This has been done by making the skirt airtight, inflating the skirt in a manner similar to a tubeless tire, or by placing one or more airtight tubes within the skirt and inflating those tube(s). All of these alternatives create problems. The first problem is that skirt material needs to be replaced more often dependent on the abrasiveness of the surface on which the hovercraft is travelling. If adhesives are used to secure the skirting material to the vehicle surface to make it airtight, replacing the skirting material becomes more challenging and correspondingly expensive. If additional airtight tubing is used, this adds cost to the hovercraft. Another problem occurs when the skirting material fails as a result of a puncture. Adding an air compressor to compensate for a puncture failure, which will likely happen during the expected life of the skirting material, is generally not feasible.
In one illustrated embodiment of the present disclosure, a hovercraft includes a hull having a base including a forward end, a rear end, and a central opening, a thrust air supply source coupled to the hull adjacent the rear end, and an inflatable skirt coupled to an outer periphery of the base to define a central lift air chamber under the hull. The hovercraft also includes a lift air supply source coupled to the hull. The lift air supply source includes a dynamic air flow area in communication with the central lift air chamber to provide continuous air flow to the central lift air chamber and a static air flow area in communication with the skirt so that air flow enters the skirt to replenish air leaking from the skirt. The static air flow area has less air flow than the dynamic air flow area. In an illustrated embodiment, the static air flow area is located at a higher position than the dynamic air flow area to reduce the likelihood of water entering the inflatable skirt when the hovercraft is operated on water.
In another illustrated embodiment of the present disclosure, a method is provided for supplying lift air to a hovercraft having a hull having a base including a forward end, a rear end, and a central opening, and an inflatable skirt coupled to an outer periphery of the base to define a central lift air chamber under the hull, The method includes providing dynamic air flow to the central lift air chamber to provide continuous lift air flow, and providing static air flow to the skirt to replenish air leaking from the skirt. The static air flow volume is less than the dynamic air flow volume.
Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.
Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of various features and components according to the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present disclosure.